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<li class="navelem"><a class="el" href="../../d5/d10/tutorial_js_root.html">OpenCV.js Tutorials</a></li><li class="navelem"><a class="el" href="../../d1/d78/tutorial_js_table_of_contents_core.html">Core Operations</a></li>  </ul>
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<div class="title">Some Data Structures </div>  </div>
</div><!--header-->
<div class="contents">
<div class="textblock"><h2>Goal </h2>
<ul>
<li>You will learn some data structures : <b>Point</b>, <b>Scalar</b>, <b>Size</b>, <b>Circle</b>, <b>Rect</b>, <b>RotatedRect</b> etc.</li>
</ul>
<p>Scalar is array type in Javascript. Point, Size, Circle, Rect and RotatedRect are object type in JavaScript.</p>
<h2>Point </h2>
<p>There are 2 ways to construct a Point and they are the same: </p><div class="fragment"><div class="line">// The first way</div><div class="line">let point = new cv.Point(x, y);</div><div class="line">// The second way</div><div class="line">let point = {x: x, y: y};</div></div><!-- fragment --><dl class="params"><dt>Parameters</dt><dd>
  <table class="params">
    <tr><td class="paramname">x</td><td>x coordinate of the point.(the origin is the top left corner of the image) </td></tr>
    <tr><td class="paramname">y</td><td>y coordinate of the point.</td></tr>
  </table>
  </dd>
</dl>
<h2>Scalar </h2>
<p>There are 2 ways to construct a Scalar and they are the same: </p><div class="fragment"><div class="line">// The first way</div><div class="line">let scalar = new cv.Scalar(R, G, B, Alpha);</div><div class="line">// The second way</div><div class="line">let scalar = [R, G, B, Alpha];</div></div><!-- fragment --><dl class="params"><dt>Parameters</dt><dd>
  <table class="params">
    <tr><td class="paramname">R</td><td>pixel value of red channel. </td></tr>
    <tr><td class="paramname">G</td><td>pixel value of green channel. </td></tr>
    <tr><td class="paramname">B</td><td>pixel value of blue channel. </td></tr>
    <tr><td class="paramname">Alpha</td><td>pixel value of alpha channel.</td></tr>
  </table>
  </dd>
</dl>
<h2>Size </h2>
<p>There are 2 ways to construct a Size and they are the same: </p><div class="fragment"><div class="line">// The first way</div><div class="line">let size = new cv.Size(width, height);</div><div class="line">// The second way</div><div class="line">let size = {width : width, height : height};</div></div><!-- fragment --><dl class="params"><dt>Parameters</dt><dd>
  <table class="params">
    <tr><td class="paramname">width</td><td>the width of the size. </td></tr>
    <tr><td class="paramname">height</td><td>the height of the size.</td></tr>
  </table>
  </dd>
</dl>
<h2>Circle </h2>
<p>There are 2 ways to construct a Circle and they are the same: </p><div class="fragment"><div class="line">// The first way</div><div class="line">let circle = new cv.Circle(center, radius);</div><div class="line">// The second way</div><div class="line">let circle = {center : center, radius : radius};</div></div><!-- fragment --><dl class="params"><dt>Parameters</dt><dd>
  <table class="params">
    <tr><td class="paramname">center</td><td>the center of the circle. </td></tr>
    <tr><td class="paramname">radius</td><td>the radius of the circle.</td></tr>
  </table>
  </dd>
</dl>
<h2>Rect </h2>
<p>There are 2 ways to construct a Rect and they are the same: </p><div class="fragment"><div class="line">// The first way</div><div class="line">let rect = new cv.Rect(x, y, width, height);</div><div class="line">// The second way</div><div class="line">let rect = {x : x, y : y, width : width, height : height};</div></div><!-- fragment --><dl class="params"><dt>Parameters</dt><dd>
  <table class="params">
    <tr><td class="paramname">x</td><td>x coordinate of the vertex which is the top left corner of the rectangle. </td></tr>
    <tr><td class="paramname">y</td><td>y coordinate of the vertex which is the top left corner of the rectangle. </td></tr>
    <tr><td class="paramname">width</td><td>the width of the rectangle. </td></tr>
    <tr><td class="paramname">height</td><td>the height of the rectangle.</td></tr>
  </table>
  </dd>
</dl>
<h2>RotatedRect </h2>
<p>There are 2 ways to construct a RotatedRect and they are the same: </p><div class="fragment"><div class="line">// The first way</div><div class="line">let rotatedRect = new cv.RotatedRect(center, size, angle);</div><div class="line">// The second way</div><div class="line">let rotatedRect = {center : center, size : size, angle : angle};</div></div><!-- fragment --><dl class="params"><dt>Parameters</dt><dd>
  <table class="params">
    <tr><td class="paramname">center</td><td>the rectangle mass center. </td></tr>
    <tr><td class="paramname">size</td><td>width and height of the rectangle. </td></tr>
    <tr><td class="paramname">angle</td><td>the rotation angle in a clockwise direction. When the angle is 0, 90, 180, 270 etc., the rectangle becomes an up-right rectangle.</td></tr>
  </table>
  </dd>
</dl>
<p>Learn how to get the vertices from rotatedRect:</p>
<p>We use the function: <b>cv.RotatedRect.points(rotatedRect)</b> </p><dl class="params"><dt>Parameters</dt><dd>
  <table class="params">
    <tr><td class="paramname">rotatedRect</td><td>rotated rectangle</td></tr>
  </table>
  </dd>
</dl>
<div class="fragment"><div class="line">let vertices = cv.RotatedRect.points(rotatedRect);</div><div class="line">let point1 = vertices[0];</div><div class="line">let point2 = vertices[1];</div><div class="line">let point3 = vertices[2];</div><div class="line">let point4 = vertices[3];</div></div><!-- fragment --><p>Learn how to get the bounding rectangle from rotatedRect:</p>
<p>We use the function: <b>cv.RotatedRect.boundingRect(rotatedRect)</b> </p><dl class="params"><dt>Parameters</dt><dd>
  <table class="params">
    <tr><td class="paramname">rotatedRect</td><td>rotated rectangle</td></tr>
  </table>
  </dd>
</dl>
<div class="fragment"><div class="line">let boundingRect = cv.RotatedRect.boundingRect(rotatedRect);</div></div><!-- fragment --> </div></div><!-- contents -->
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